This section will continue to probe the protective effect of milk against a common mucocutaneous - respiratory virus, herpes simplex virus (HSV). We shall characterize humoral protection against HSV by immunospecific and nonspecific factors of colostrum in vitro. Methods of characterization include HSV neutralization, and several anti-HSV antibody assays including antibody-dependent cellular cytotoxicity, ELISA, and Western blot. These factors will then be longitudinally analyzed in milk of breast-feeding mothers. The non-antibody neutralizing activity will be molecularly characterized. Finally the milk anti-HSV activity will be correlated with in vivo acquisition of HSV by human infants in a longitudinal seroepidemiologic study of HSV acquisition in Mexico. We shall continue to analyze possible protection against HSV by milk leukocytes by defining the defects in cellular cytotoxic effector function on a molecular level. Regeneration of cytotoxic actively will be attempted in vitro ad in vivo. Recently described leukocyte-released factors such as interleukin-2 (IL-2), an IL-2 suppression factor, gamma interferon, and our colostral cytokine will be analyzed regarding production by colostral and milk cells. The effect of these factors will be tested in vivo on a model system of neonatal HSV infection. These studies will discern factors in milk which protect against HSV infection in infants. They may point toward rational methods of milk banking or supplimentation to enhance the resistance of infants to viral infection.